How Accurate Are Population Data?

The accuracy of population data counted by censuses varies enormously across the world

World Economics
7 November 2019

Accurate population data on the total number of individuals living in a country, the demographic breakdown by age and gender and their geographical distribution is extremely important. International differences in the relative standard of living across countries are assessed by development institutions such as the World Bank by calculating GDP per capita. At the national level in most countries, population counts are used to apportion funds between local governments, to allocate voting districts for national parliaments and to determine policy needs. Accurate urban population and rural estimates are vital for planning purposes particularly to forecast the pressures on transport, water and sewage, energy infrastructure and housing needs. 

Unfortunately, the accuracy of population data counted by censuses varies enormously across the world. The problem is particularly serious in Africa where GDP data is also of extremely poor quality making GDP per capita estimates of dubious value for most purposes. A paper by Deborah Potts published in World Economics in 2011 cast serious doubts on the accuracy of urban population estimates across Africa. 

Only a census can provide accurate population data. The United States was the first country in the modern age to undertake a census in 1790, but this was closely followed by European countries including the United Kingdom which introduced its first census in 1801. Now most countries conduct regular census counts, but the regularity and the accuracy varies, especially in Africa and Asia. 

Currently, the UN World Population and Housing Census Programme recognises Population and Housing Censuses (PHCs) as a main data source needed for policies and programmes aimed at inclusive socioeconomic development and environmental sustainability. They are also an important source for supplying dis


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